There is an electron microscope as an observation device for magnifying a sample surface topology. The operation of a scanning electron microscope (in the following, referred to as an SEM) is shown. Primary electrons accelerated by a voltage applied to an electron source are focused at an electron lens, and the focused primary electrons are scanned over a sample using a deflector. Secondary electrons emitted from the sample by irradiating the primary electrons are detected at a detector. Secondary electron signals are detected in synchronization with scanning signals to form an image. The amount of the secondary electrons emitted from the sample is varied depending on the sample surface topology.
In the case where a sample is an insulator, the sample surface inevitably becomes charged due to the irradiation of electrons. Charging due to the irradiation of electrons causes an image drift under observation, for example, to produce an image failure.
A method is known as a method for addressing an image failure caused by the charging in which an electric conductor is coated over the sample surface. Metals such as gold and platinum are used for the electric conductor. Moreover, Patent Literature 1 discloses a method in which a sample is applied with an ionic liquid hardly volatilized in a vacuum to provide electrical conductivity on the electron irradiation surface. Furthermore, Patent Literature 2 discloses a low-energy SEM that can provide stable observation using low-energy electrons even with charging.